Disable load balancing on dual PRIs - 3640 with MICA modems for dial out

Question

We have a custom application that connects through reverse telnet to a Cisco 3640 that has 2 NM-24DM modules and 2 PRIs connected to it. Currently all outgoing calls are getting load balanced over the two PRIs. I need to change that so that all calls go over the first PRI and when all channels are used up, it starts using the second PRI. Seems like a simple enough thing to do but I can't figure out how to.
Here is my config
Current configuration : 1401 bytes
version 12.4
service timestamps debug uptime
service timestamps log uptime
service password-encryption
hostname DIALOUT01
boot-start-marker
boot-end-marker
enable secret 5 xxxxxxx
no aaa new-model
clock timezone EST -5
clock summer-time EDT recurring
no ip routing
no ip cef
no ip domain lookup
ip domain name xxxxxxx.xxx
isdn switch-type primary-ni
controller T1 0/0
framing esf
linecode b8zs
pri-group timeslots 1-24
description xxxx
controller T1 0/1
framing esf
linecode b8zs
pri-group timeslots 1-24
description xxxx
interface FastEthernet0/0
ip address dhcp hostname dialout01
no ip route-cache
no ip mroute-cache
duplex auto
speed auto
interface Serial0/0:23
no ip address
encapsulation hdlc
isdn switch-type primary-ni
no fair-queue
no cdp enable
interface Serial0/1:23
no ip address
encapsulation hdlc
isdn switch-type primary-ni
no fair-queue
no cdp enable
no ip http server
control-plane
line con 0
line 33 56
modem InOut
modem autoconfigure type mica
transport preferred telnet
transport input telnet
transport output telnet
line 65 88
modem InOut
modem autoconfigure type mica
transport preferred telnet
transport input telnet
transport output telnet
line aux 0
line vty 0 4
password 7 xxxxx login
end
Thanks,
Shahid

Answer 1

If I understand the question I think that isdn  bchan-number-order is the command you are interested in.  I think it detaults to round-robin, sounds like you want ascending (that is isdn  bchan-number-order ascending).  It is an interface subcommand.
See  http://www.cisco.com/en/US/docs/ios/12_3t/12_3t2/feature/guide/gt_ibcac.html#wp1055853
That may only apply to native ISDN calls and not MICA based calls, but see if that helps.